1. Field of the Invention
This invention relates to a velocity control servo system, and, more particularly, to a circuit for increasing the accuracy, response and operating speed range of a velocity control servo system.
2. Description of the Prior Art
Prior art velocity control servo systems have in the past used a simple velocity loop that compared a commanded velocity signal, which is indicative of the desired velocity of movement of a member being controlled, with a signal indicative of the actual velocity of the member. Such a simple servo loop provided reasonably accurate dynamic and static control over a member which is moved by a motor over a maximum speed range having a ratio of approximately 1,000:1. In other words, reasonable control over speed and accuracy could be maintained as the speed of the motor varied from 1 RPM to a maximum of 1,000 RPM, or from 0.1% of the maximum speed to 100% of maximum speed of the motor. While such a range of control over the speed of the motor and the member being driven by the motor is acceptable for certain applications, there are other applications which require the range of speed over which accurate control can be maintained by the servo system to be at least a ratio of 10,000:1 or at times even exceed a ratio of 50,000:1.